1. Field of the Invention
The present invention relates to an information input apparatus, and more particularly to an information input apparatus provided with a photoelectric transducer.
2. Description of the Prior Art
Information input apparatus with solid-state photoelectric transducer are applicable for television cameras, an input unit for facsimile, digital copiers etc., or reading apparatus for characters or other images, and have been the subject of active development in recent years.
Such information input apparatus generally comprises a group of picture elements each having a photoelectric transducing function and a circuit having a scanning function for obtaining the electric signals from said picture elements in time-sequentially arranged form, and many utilize a combination of photodiodes and MOS-FET or metaloxide semi-conductor field-effect transistors (such combination being hereinafter referred to as MOS-type imaging device) or a CTD (charge transfer device) such as a CCD (charge coupled device) or a BBD (bucket brigade device).
However, in such MOS-type imaging device or CTD which has to be formed on a single crystal silicon wafer, the light-receiving area of the photoelectric transducer is limited by the dimension of the available single crystal silicon wafer. Thus, in the present status of the art which only allows manufacture of a satisfactorily uniform single crystal silicon wafer of several inches in diameter at maximum, the dimension of the light-receiving area of such MOS-type imaging device or CTD formed on such wafer can never exceed the above-mentioned dimension of the single crystal silicon wafer.
Consequently, in case there is employed an information input apparatus utilizing a photoelectric transducer of such limited light-receiving area for the optical information input for example into a digital copier, it becomes indispensable to place an optical system of an elevated reduction rate between an original to be copied and the light-receiving face, thereby focusing the image of said original within the light-receiving area.
Such arrangement requires a certain amount of light path length which is decisively unfavorable for the compactization of the entire apparatus.
As an alternative, there is also proposed an arrangement in which plural photoelectric transducers are aligned in such a manner that the longitudinal length of entire light-receiving areas is equal or approximately equal to the length in the principal scanning direction of the maximum length copiable and the image of the original is divided into the partial sections of a number corresponding to that of the photoelectric transducers, whereby the optical path length is reduced for the compactization of the apparatus.
However such arrangement is still defective since the alignment of plural photoelectric transducers inevitably forms light-insensitive boundary areas therebetween, thus resulting in an discontinuous light-receiving area, whereby the optical image of the original is divided into small portions and the image corresponding to said boundary portions is not entered into the photoelectric transducers, so that the resulting copy either has unimaged white stripes or is composed of incomplete combination of image fragments not containing such white stripe portions. Also as the optical image on each photoelectric transducer is optically inverted, the entire image formed on said photoelectric transducers is different from the optically inverted image of the original. For this reason the reproduction of the original image cannot be achieved by simply reproducing said entire image.
In addition to the foregoing, the number of lead electrodes connecting the photoelectric transducer with other electric circuits is in the conventional technology at least equal to the sum of the number of picture element electrodes and that of counter electrodes and increases with the increase in number of the picture elements. Consequently the conventional technology cannot be free from the limitation of complexity in the electric bonding and other manufacturing procedure and also from the requirement for the high-precision manufacturing technology, which increase the mass production and cost reduction.
As explained in the foregoing, the information input apparatus utilizing conventional photoelectric transducer is associated with various drawbacks yet to be solved, including the aforementioned requirement for the optical system of an elevated image reduction rate resulting from the limited dimension of the light-receiving face and giving rise to a significantly large optical path length, thus rendering the compactization extremely difficult.
For this reason there has been required an information input apparatus provided with a photoelectric transducing unit having a light-receiving face of an expanded length and of an improved resolution. Particularly for the applications in facsimile or digital copier or in the character or image reading apparatus, indispensable is an information input apparatus provided with a photoelectric transducing unit having a light-receiving face of a dimension equal or approximately equal to the size of the original to be reproduced and of a resolving power sufficient for faithful reproduction of the original image.